Clinical outcomes and safety study of CDK4/6 inhibitors in hormone-positive metastatic breast cancer - A real-world tertiary cancer center experience.

BACKGROUND

CDK4/6 inhibitors have become the standard of care for the treatment of HR+ metastatic breast cancer (MBC) based on clinical trials. However, real-world experience and efficacy in various subgroups are still lacking. Therefore, we conducted a study to analyze the use of CDK4/6 inhibitors in the treatment of HR-positive MBC and assess the related outcomes.

METHODS

A total of 120 patients who received CDK4/6 inhibitors from 2015 to 2021 were analyzed. Detailed clinical, demographic information and tumor-related factors were obtained for each patient. Progression-free survival (PFS), toxicity profile, and tolerance to CDK4/6i were analyzed and correlated.

RESULTS

Among the 120 patients analyzed, 100 received palbociclib, while ribociclib, and abemaciclib were given to ten patients each. The median age of the population was 57 years. With a median follow-up of 28 months, the median PFS and overall survival (OS) were 25 and 54 months, respectively. The PFS did not significantly differ among different anti-hormonal agents used in combination with CDK4/6 inhibitors. Patients who were resistant to endocrine therapy had a shorter PFS compared to treatment-naive MBC patients (22 versus 40 months). Patients with strong hormonal receptor expression had a significantly better PFS compared to those with weak expression (25 versus 14 months). Her2Neu-negative patients responded better than those with low positive expression (P = 0.039). Visceral metastatic disease was associated with a significantly shorter PFS (17 months) compared to skeletal metastasis (32 months). There was no statistical significance when CDK4/6 inhibitors were used in different lines of treatment or with dose reduction.

CONCLUSION

CDK4/6 inhibitors demonstrate similar responses and better tolerance in real-world evidence. Further studies are necessary to identify other predictive and resistance factors for the use of CDK4/6 inhibitors.